AMILORIDE SUPPRESSES ERYTHROPOIETIN-INDUCED PROLIFERATION AND MAP KINASE, BUT POTENTIATES DIFFERENTIATION OF J2E CELLS

The J2E erythroid cell line proliferates and differentiates in respons e to erythropoietin (epo). Here we demonstrate that the diuretic amilo ride can suppress normal and hormone-induced cell division in a dose-d ependent manner. In the presence of amiloride, cell numbers did not in crease, [H-3]thymidine incorporation decreased, and fewer cells were o bserved in the S, G(2), and M phases of the cell cycle. In addition, t he levels of proliferating cell nuclear antigen, a subunit of DNA poly merase delta, fell. In marked contrast, epo-initiated differentiation was potentiated when J2E cells were cultured with the drug: the number of benzidine-positive cells increased, hemoglobin content per cell ro se, and more morphologically mature cells were produced. Immunoblottin g with anti-phosphotyrosine antibodies revealed that amiloride reduced the number of phosphorylated proteins in epo stimulated cells. Moreov er, the protein content of p42 and p44 MAP kinases was noticeably down regulated in amiloride-treated cultures. These data indicate that amil oride may interfere with epo-induced signaling cascades within J2E cel ls which result in restricted cell division and promotion of maturatio n. (C) 1995 Academic Press, Inc.